1. Field of the Invention
The present invention relates to the technical fields of a lens moving mechanism and an imaging apparatus and more particular, to the technical field of achieving a reduction of power consumption and the prevention of backlash at the time of a movement of a lens holder by providing a magnetic body attracting a drive magnet attached to the lens holder.
2. Description of the Related Art
As disclosed in Japanese Patent Application Publication (KOKAI) No. 2002-169073, some imaging apparatuses, such as a video camera and a still camera severally have a moving lens for zooming or focusing in a lens-barrel that is held in a lens holder.
In the imaging apparatus described in the patent document JPA No. 2002-169073, a drive coil is attached to the lens holder freely movably supported by a couple of guide shafts extending in an optical axis direction, a yoke is fixed in the lens-barrel, and a drive magnet is fixed to oppose to the drive coil.
In such an imaging apparatus, when the drive coil is electrified, an impelling force into a direction according to the electrification direction is given to the lens holder by the drive magnet and the drive coil, and the lens holder and the moving lens are moved into the optical axis direction while being guided by guide shafts. Consequently, focusing adjustment or zooming adjustment is performed by the movement of the moving lens into the optical axis direction.
Now the imaging apparatus such as the video camera, the still camera frequently performs photographing in a state of being grasped by a user. The imaging apparatus is sometimes made so as to be inclined into a left, a right, an up or a down direction according to the grasping state of the user, or is a photographing angle. In some inclination direction of the imaging apparatus, the optical axis direction of the moving lens inclines to the horizontal direction. At this time, for example, if the optical axis is directed to be in the vertical direction or in a direction close to the vertical direction, the lens holder and the moving lens move into the optical axis direction (downward) owing to their self weights, and consequently the focusing adjustment and the zooming adjustment may be hindered.
Consequently, when an inclination in the optical axis direction as described above arises at the time of photographing, it is required to regulate the movement in the optical axis direction of the lens holder holding the moving lens to hold the lens holder. However, the conventional imaging apparatus performs the holding of the lens holder by constantly electrifying the drive coil. Consequently, the conventional imaging apparatus has a problem of large power consumption.
On the other hand, because a clearance for securing the smooth movement of the lens holder exists between the guide shafts and the bearing portion of the lens holder supported by the guide shafts freely slidably, the lens holder moves in the direction perpendicular to the optical axis by the clearance, and there is the possibility that a backlash of the lens holder occurs with regard to the guide shafts.
When the backlash of the lens holder occurs, the so-called image shaking phenomenon, in which a photographed image shakes, occurs. For example, a backlash quantity of several microns in the lens holder may possibly be an image shaking of a magnitude within a range of from 5 mm to 10 mm on a monitor of 21 inches.